1. Field Of The Invention
This invention relates to a removable key for a wrenching tool, and in particular, to a key for use in a wrenching tool for attachment of frangible fasteners.
2. Brief Statement Of The Prior Art
Frangible fasteners are used extensively in the aerospace industry. These fasteners employ a threaded nut member which has a threaded collar and a distal wrenching ring separated by a notched section that shears from the collar when the applied torque exceeds a predetermined torsional loading. Often the threaded collar has an upset portion, usually a slightly elliptical shape, to provide a frictional spring lock to prevent the fastener from spinning off in the event that the residual tension on the fastener is lost.
These fasteners are applied with wrenching tools which have a center key that is inserted into a broached keyway of the fastener bolt to immobilize the bolt onto which the collar is applied. Typically the key is slidably mounted in the wrenching tool concentric with the driven, outer, socket member. Usually the key is fixed in the tool with a set screw, however, some tools, such as shown in U.S. Pat. No. 3,584,527, permit the key to be inserted from the rear of the tool through a port closed with a removable retainer plate. In U.S. Pat. No. 2,239,072, a tool is illustrated in which the key is retained with a ball detent which has a clamp ring that secures the detecting ball in a groove about the shaft of the key. All of these prior devices have required a partial disassembly of the tool to remove or change keys.
The attachment of keys in the prior tools is cumbersome and causes delays and difficulties in changing the tools between applications of fasteners in interference fits and loose fits, since only in the latter instances is a key necessary. It is often necessary to replace broke and worn keys, and this is a time consuming operation in the prior tools which must be partially disassembled to release the key. A key occasionally jams in a bolt, which immobilizes the tool, and difficulties are usually experienced in attempting to release the key from the tool.